HK1184581A - Polycarbonate radiofrequency identification device, and method for manufacturing same - Google Patents

Description

Polycarbonate radio frequency identification device and method for manufacturing same

Technical Field

The present invention relates to the field of value security documents and objects comprising contactless data exchange electronics, and in particular to Radio Frequency Identification Devices (RFID) and methods of manufacturing thereof.

Background

A contactless Radio Frequency Identification Device (RFID) is a device mainly composed of an antenna embedded in a device substrate and a chip connected to an antenna connection contact. These devices allow the exchange of information with the outside world by means of a remote, and thus contactless, electromagnetic coupling between their antenna and a second antenna located in the associated reading device. These devices are used today for a large number of applications, in particular to identify zones acecs in controlled access areas) Or persons moving from one area to another. The device is typically formed on a flexible planar substrate, in the form of a bank card or a form adapted to be able to be inserted into a value or security document. Such RFID devices are commonly referred to as "embedded". Typically, the chip is connected directly to the antenna contacts by a "flip-chip". However, the chip may also be packaged in a module for better protection.

Information is exchanged between the RFID device and the reader, in particular information stored in the chip that is processed, for example upon identification of the holder of the object in which the RFID device is located, and permission thereof to pass through the controlled access area.

Currently, these RFID devices can be manufactured according to several manufacturing methods. There is interest in RFID devices whose antennas are realized by printing on thermoplastic substrates. One of the methods involves laminating several layers of different materials together, such as paper for the antenna substrate and thermoplastic materials for the upper and lower layers. The RFID device obtained by such a method has a disadvantage of peeling in its thickness and, therefore, is not suitable for use for many years in the case of an identification card or the like. On the other hand, the use of the same material, such as a thermoplastic material, for all three layers does not solve the peeling problem and causes problems in lamination. In fact, insufficient flexibility and elasticity of the layers that are stacked together can crack the antenna and, thus, break the electrical connection between the antenna and the chip when mounted under pressure. In addition, mounting at a higher temperature in the lamination step may deform the substrate, which may also result in severe cracking of the antenna due to the large thickness of the coil intersections due to the double thickness of the conductive material forming the coils and the insulating material isolating and insulating the coils from each other.

In addition, RFID devices based on wire-wound antennas do not comprise the same drawbacks, since the copper wire does not break under pressure, but has a tendency to be moulded in thermoplastic materials. In addition, its thickness is small, about 25 μm, and since the copper wire is shielded and thus insulated, its use allows to avoid overlapping the insulating layer between the coils and to obtain a thickness margin of about 50 μm at the position where the coils cross, thus being less constrained.

Disclosure of Invention

It is therefore an object of the present invention to provide a method of manufacturing an RFID device in which the antenna is realized by printing on a thermoplastic material, solving the problem of cracking of the printed antenna during the lamination step.

It is a further object of the invention to provide an RFID device which does not risk peeling over time.

Thus, the object of the present invention is a method of manufacturing a Radio Frequency Identification Device (RFID) comprising a planar substrate with an antenna and a chip connected to the antenna, said antenna being formed by a winding of a plurality of turns, the antenna comprising crossing areas of coils, insulating strips of dielectric material separating overlapping antenna coils at the crossings, the method comprising the steps of:

a) the step of realizing an antenna comprising printing a coil, two conductive ink connection contacts, and an insulating strip of dielectric material at the intersection of the coils, and comprising subjecting the substrate to a heat treatment so as to sinter the ink,

b) connecting the chip on the substrate from the antenna side,

c) superposing a second layer on the substrate from the antenna side, the second layer including a first opening concentrated on the chip and a second opening concentrated on the insulating tape at the cross region of the antenna,

d) the third layer is superimposed on the second layer,

e) the three layers are laminated together.

Drawings

The objects, objects and features of the present invention will become more apparent upon reading the following description with reference to the accompanying drawings. In the drawings:

FIG. 1 shows a front view of a layer supporting a radio frequency device;

FIG. 2 shows a cross-sectional view of the support layer of the RF device of FIG. 1 along the A-A axis;

fig. 3 shows a front view of a second supporting layer of an RFID device according to the invention; and

fig. 4 shows a cross-sectional view of a radio frequency device according to the invention.

The components shown in the figures are not drawn to true scale.

Detailed Description

In fig. 1, a top view of a credit card form base plate 10 is shown. In the following description, the substrate denotes an antenna substrate. The base plate conforms to the ISO form, but it may also have other dimensions, and it takes the form of, for example, a strip or a plate comprising a plurality of base plates to be cut into ISO form. A sub-layer 12 of thickness 5 μm is provided on the antenna substrate 10 over the area shown in dark in fig. 1. The sub-layer is realized, for example, by printing of ink, resin or lacquer. According to one embodiment, the sub-layer 12 is realized on the basis of a colored transparent ink for visual localization. According to a preferred embodiment of the present invention, the antenna substrate 10 is made of Polycarbonate (PC). The antenna 11 comprises a winding of several turns, two connection contacts 17 and 18 at the two ends of the winding, and a bridge 13, the antenna 11 being printed on the antenna substrate 10 on the sub-layer 12 and not leaving the area defined by the sub-layer. As shown in fig. 1, the size of the area of the sub-layer 12 preferably slightly exceeds the footprint of the antenna. Thus, the shape of the area is directly determined by the shape of the antenna.

The coils and the connection contacts of the antenna are realized by screen printing, flexographic offset printing, gravure printing, offset printing or ink-jet methods, conductive inks based on the epoxy ink type filled with conductive particles (for example, silver or gold) or on conductive polymers. According to another embodiment, the sub-layer 12 is absent and the antenna is printed directly on the antenna substrate. In both embodiments, i.e. with and without sub-layers, the antenna is printed in several passes. The first pass comprises the two connection contacts 17 and 18 of the printed antenna and the bridge 13, which is generally referred to as a "bridge". The second pass comprises printing an insulating strip 16 of dielectric material overlying the bridging bridge. The third pass comprises printing coil windings with inner and outer ends 14 and 15 passing over and crossing the bridge 13 to be electrically connected as a whole. The insulating strip 16 thus allows to obtain an antenna crossing area in which the bridge 13 and the antenna coil cross without the risk of short-circuits. The overlap of the crossed coils and the dielectric reaches a thickness between 70 and 75 μm.

An opening 19 is made in the antenna substrate between the connection contacts 17 and 18. The opening is achieved with a laser or with a punch (indicia pi ce).

According to fig. 2, the integrated circuit module 29 comprises a chip 25, at least two connection regions 23 and 24. The connection between the chip and the regions 23 and 24 is made with wires or connection cables 26, commonly referred to as "wire bonds". The chip 25 and the wires are encapsulated in a protective resin 27 based on a material that is resistant to stress and is not electrically conductive. The package 27 (or "molded") is a rigid housing formed in any manner that surrounds the chip and its wiring so as to make it less fragile and easy to handle. The package has a thickness between 200 and 240 μm. The module then has a flat surface on its upper surface corresponding to the upper part of the encapsulation 27 and contact areas 23 and 24 on its lower surface for connection to the circuit. The contact regions 23 and 24 are made of an electrically conductive material, such as aluminium, with a thickness between 70 and 100 μm.

The module 29 is glued to the antenna substrate layer 10 by means of two contacts of adhesive material 33 and 34 arranged on one side of the antenna connection contacts or riding over the antenna connection contacts 17 and 18. The module is positioned such that the connection contacts 17 and 18 face the contact areas 23 and 24 of the module and such that the encapsulation part or encapsulation 27 of the module is located in the cavity 19. In particular, a portion of the connection contacts 17 and 18 will abut against a portion of the contact areas 23 and 24 which is not covered by the adhesive material. The adhesive material for the contacts 33 and 34 is an adhesive such as: the module is only fixed to the substrate layer 10 and does not directly participate in the electrical connection between the module and the antenna, since the adhesive is non-conductive. The adhesive utilized is of the thermally crosslinkable epoxy type not filled with conductive particles. Adhesive contacts are provided on the substrate layer 10 in the vicinity of the antenna contacts so that when the module 29 is placed into the cavity 19 the adhesive of the contacts is crushed by a small part of the contact area of the module until another part of the contact area becomes in contact with the antenna contacts. At this point, the adhesive contact reaches the same thickness, or substantially the same thickness, as and touches the antenna contact. This operation, which involves placing the module in the cavity, is accompanied by a heating phase of the contact zones of the module, which allows the adhesive to crosslink. The adhesive contacts harden under the effect of heat, thus keeping the areas 23 and 24 of the module in contact against the connecting contacts. This sintering (cuisson) step of the adhesive is achieved locally by applying a heating resistor without applying pressure on the module contact areas.

The close contact of the contact areas 23, 24 of the module and the connection contacts 17, 18 of the antenna ensures the reliability of the electrical connection. Thus, from the mounting of the module 29 in the cavity 19, an electrical connection is achieved by the contact areas 23, 24 of the module being in direct contact with the connection contacts 17 and 18 of the antenna. The substrate thus obtained is an antenna substrate having a module integrally connected to the substrate and electrically connected to an antenna. Thus, the electrical connection has the advantage of being achieved without soldering and without supplying material.

According to one embodiment of the invention, the connection contacts 17 and 18 of the antenna have a concave or hollow or ring-shaped hollowed-out form, so that the adhesive material contacts 33 and 34 are placed inside the hollow of the concave or inside the hollowed-out part. In a preferred embodiment of the invention, the antenna contacts are U-shaped, so that the contacts of the adhesive material are placed inside the U-shape.

According to fig. 3, a top view of the second layer 20 is shown. The second layer is a Polycarbonate (PC) layer with a thickness between 50 and 60 μm and the same width and length as the first antenna substrate layer 10. Two openings 26 and 39 are realized in this layer by means of a laser or by means of a punch. The two openings are cavities that traverse the entire thickness of the layer 20. The openings 26 are located on the layer 20 such that: when the layers 20 cover the layer 10 by overlapping each other edge to edge, the insulating tape 16 is present in the space left by the openings 26. In this way, the openings 26 are concentrated on the insulating tape. Also, the openings 39 are located on the layer 20 such that: when the layer 20 covers the layer 10 by overlapping each other edge to edge, the portion between the connection contacts and a portion of the connection contacts are present in the space left free by the opening 39. Thus, the openings 39 are concentrated on the module 29.

Fig. 4 shows the antenna substrate 10, the second layer 20 and the third layer 30 in cross-section along the axis a-a of fig. 1. According to the method of manufacturing the device of the invention, the layer 20 is positioned on the substrate 10 such that the outer surface of the module, and thus the outer surface of the contact area comprising the module, is in the opening 39. A third layer 30 is also located on layer 20. Layer 30 is a Polycarbonate (PC) sheet of the same size as the other two layers, having a thickness between 90 and 120 μm, and preferably equal to 100 μm. Fig. 5 illustrates the antenna substrate 10, the second layer 20 and the third layer 30 of fig. 2 along the axis B-B in cross-section. In the step of positioning the layers 20 and 30 on the antenna substrate 10, the insulating tape 16 will be received in the aperture 26.

The next step involves laminating layers 10, 20 and 30 together. Thus, the three layers are subjected to a temperature increase and a pressure increase up to 180 ℃. During lamination, the intermediate layer 20 softens at a lower temperature than the lower layer 10 and the upper layer 30. Due to the pressure applied during the lamination step, the air trapped between the layers, in particular in the openings 26 and 39, is evacuated and replaced by softened polycarbonate. In this manner, the polycarbonate of the intermediate layer 20 fills the apertures during the lamination step. The layer 20 with these two apertures avoids (viter) and compensates for the excessive thickness due to the crossing area of the antennas on the one hand and the modules on the other hand.

At the end of this lamination step, the three layers 10, 20 and 30 are joined together, as shown in fig. 6. Once bonded together, these polycarbonate layers no longer differ in the thickness of the resulting RFID device, so that there is no possibility of any peeling in thickness. The antenna 11, comprising the coil, the two connection contacts 17 and 18 and the bridge 13, is completely embedded in the polycarbonate of the three layers 10, 20 and 30 that are bonded together. The edges of the RFID device according to the invention are uniform and do not have a border parallel to the upper edge 62 and the lower edge 61, which may presume that several layers are assembled to each other; this makes it impossible to attempt to peel the device through its thickness.

According to one variant of embodiment of the invention, the integrated circuit module is replaced by a bare chip of the type of chip 25 packaged in the module. According to this variant, which is not shown in the figures, the steps of implementing the antenna and of laminating the layers to each other are identical to the steps of the implementation described for the integrated circuit module.

However, the opening 19 is not necessary in the case of a chip. Openings 26 and 39 are made in layer 20 in the same way; the openings 39 are concentrated on the chip. The connection of the chip to the antenna is carried out according to a method of the type described in patent application FR2826153 by the applicant. The adhesive dielectric material is arranged on the antenna substrate 10 between the connection contacts 17, 18 of the antenna and the chip is positioned on the antenna substrate so that the contacts of the chip should abut against the connection contacts of the antenna. The viscous material is then subjected to a heat treatment to harden it.

In this embodiment, when the chip is connected to the antenna, the pressure exerted on the chip allows the contact areas of the chip, commonly referred to as "bumps" (bump), to penetrate into the connection contacts of the antenna, which are deformed and thus ensure a better connection between the chip and the antenna.

The RFID device according to the invention forms a planar substrate which can be integrated in a security document, such as an identification card, an identification document, a driver's license, a pass card or the like.

The RFID device according to the invention has the advantage of a thickness between 0.38 and 0.41mm and supports laser etching.

Claims (11)

1. A method of manufacturing a Radio Frequency Identification Device (RFID) comprising a planar substrate having an antenna (14) and a chip (25) connected to the antenna, the antenna being formed by a winding (11) of a plurality of turns, the antenna comprising a crossover region of coils, an insulating strip (16) of dielectric material separating overlapping antenna coils at the crossover, the method comprising the steps of:

a) -a step of realising an antenna comprising printing a coil, two conductive ink connection contacts (17, 18), and an insulating strip (16) of dielectric material at the coil intersection, and comprising subjecting the substrate to a heat treatment in order to sinter the ink,

b) connecting the chip (25) on the substrate (10) from the antenna (14) side,

c) overlapping a second layer (20) on said substrate from the antenna side, the second layer comprising a first opening (39) concentrated on the chip and a second opening (26) concentrated on said insulating strip (16) at the crossing area of the antenna,

d) overlapping the third layer (30) on the second layer,

e) the three layers (10, 20, 30) are laminated together.

2. The method according to claim 1, wherein said layer (10, 20, 30) is made of Polycarbonate (PC).

3. A method according to claim 1 or 2, wherein step b) comprises the steps of:

b1) depositing a viscous dielectric material between said connection contacts (17, 18) of the antenna,

b2) placing the chip (25) such that the contact area of the chip abuts against the connection contacts (17, 18) of the antenna,

b3) the viscous material is subjected to a heat treatment to harden the viscous material.

4. A method according to claim 1 or 2, wherein step b) comprises the steps of:

b1) an aperture (19) is realized between said connection contacts (17 and 18) of the antenna,

b2) depositing an adhesive dielectric material (33, 34) on a portion of said connection contacts (17, 18) of the antenna,

b3) placing the chip encapsulated in a module (29) such that the contact areas (23, 24) of the module (29) abut the connection contacts (17, 18) of the antenna and the encapsulation (27) of the module is located in the cavity,

b4) subjecting the viscous material (33, 34) to a heat treatment to harden the viscous material.

5. Method according to claim 4, wherein the connection contacts (17, 18) of the antenna are U-shaped.

6. Method according to claim 1, wherein said opening (19, 26, 39) is carried out by means of a laser or a punch before the step of overlapping the layers with each other.

7. Method according to claim 4 or 5, wherein the adhesive material (33, 34) is an epoxy type adhesive capable of thermal crosslinking.

8. The method according to one of claims 2 to 8, wherein the polycarbonate of each layer (10, 20, 30) is transparent.

9. Method according to one of the preceding claims, wherein step a) comprises the following steps:

a1) printing a sub-layer (12) of a material mainly consisting of lacquer on a predetermined area on the antenna substrate (10) support, said area corresponding to the footprint of the antenna or being slightly larger than the footprint of the antenna,

a2) -printing an antenna on the sub-layer (12).

10. Method according to claim 9, wherein said sub-layer (12) is realized on the basis of a colored transparent ink for facilitating visual localization.

11. A Radio Frequency Identification Device (RFID) obtained according to one of the preceding claims, comprising a flexible planar substrate made of polycarbonate, the substrate having a conductive ink antenna (14) fully embedded in the polycarbonate and having a chip (25) or integrated circuit module (29) connected to the antenna, said antenna being formed by a winding of a plurality of turns, the antenna comprising crossing areas of the turns and insulating strips (16) of dielectric material separating the overlapping antenna turns at the crossings, the edges of the device being fully conformed so that any border lines between the different layers are not visible, thereby preventing any peeling attempts over the thickness of the device.